The invention applies to the grading of large batches of various kinds of fruit on the basis of carefully graded samples. It can be used with many kinds of fruits, including drupes, but it will be helpful to use a specific example, and for that purpose the handling of canning tomatoes affords a good basis for description.
Tomatoes grown for canning are mechanically harvested with culling and sorting taking place on the harvester, so that most unsatisfactory fruit is discarded. However, among the selected tomatoes there are often tomatoes which should have been culled but were not, for whatever reason. There may be some tomatoes with worm damage, some with mold, some that are not ripe, and so on. Also, depending on field conditions there may be dirt, trash, leaves, or other materials than tomatoes among the selected tomatoes. Therefore, the harvested tomatoes packed at random into very large trailers pulled by trucks, are taken to an inspection station for grading. The inspection there determines whether the canner will accept or reject each trailer load, and if the load is accepted, it is graded for quality in order to determine how much the grower is to be paid per ton.
The inspection stations are typically open-air, pole-type platforms at a height equal to that of a flat-bed truck trailer, this being the height needed for a bulk-load sampler to deliver fruit to the grading tables. The value of the annual tomato crop currently brought to such inspection and grading stations is approximately $380,000,000. The percent of off-grade fruit in a load is deducted from the payment the grower receives from the processor. The best loads of tomatoes are normally canned as whole tomatoes, while lower grades may be used for tomato sauce, ketchup, and the like.
Since each truck trailer holds several tons of fruit, it is not practical to inspect every tomato individually at the inspection station, though they may be handled individually at the cannery. Therefore, samples are employed, usually four samples per load, one sample being taken from the center of the trailer, and additional samples being taken from near its corners. The sampler itself may be that shown in the O'Brien et al. U.S. Pat. No. 3,683,702 which issued on Aug. 15, 1972. Each sample of about fifty pounds is then divided into two approximately equal portions, one portion being checked for certain types of defects and the other portion for different characteristics, such as peelability and soluble solids.
The present invention is concerned with an overall grading system and also with checking a sample for certain grade defects, including worm damage, unripeness, mold, dirt and trash, and miscellaneous defects that may relegate the load to limited use at the cannery.
The sample is taken on the basis of volume, using the sampler described in U.S. Pat. No. 3,683,702 in conjunction with normal spillover processes. Each such sample has a nominal weight, but that weight is only approximate and the approximate weights vary so much that the results of assuming that the sample weighs a particular amount leads to consequential inaccuracies that may be unfair or even disastrous, either to the grower or to the canner.
For example, a nominally "hundred pound" sample, when taken on the basis of volume, may typically vary from a low of about eighty-eight pounds to a high of about one hundred twelve pounds. When the "grade defect" materials are weighed, their actual weight has heretofore been compared with the sample as though the sample weighed exactly one hundred pounds. However, if the sample happened to be small, say weighing only eighty-eight pounds, the canner might have been misled into accepting a batch of fruit that should have been rejected or grading it too high; contrariwise, if the sample happened to weigh one hundred twelve pounds, the chances of grade defect products exceeding the tolerable weight limit were greater, so that the grower might have been paid much less than he deserved or might have had the entire batch rejected, simply because the true weight of the sample was not known and was assumed to be exactly one hundred pounds.
Thus, it is important to weigh each such sample accurately before comparing it with the weight of the grade-defect portions.
The invention therefore provides a weighing system between the bulk load sampler and the grading table. A rugged, yet accurate, weighing system is necessary, one that can be accurate despite water spray, dust, tomato vines, wind, temperature extremes, multiple operators, and large broadband vibrational forces on the inspection platform. In such environments, it appears that the best results can be obtained from scales incorporating a weigh hopper suspended from a direct-weighing overhead electronic load cell. Simplicity, low maintenance, isolation from contamination, and relatively low cost are some of the factors that favor such a system at inspection stations for processing tomatoes.
A disadvantage of direct-weighing load cells in the stated environment is that traditional manners of use do not protect them adequately from shock loads. Scales with naturally large displacements or traditional lever arrangements typically use dashpots to provide shock load protection. The extremely small displacement of direct-weighing electronic load cells prevent the generation of sufficient damping force by a dashpot. To give load cells solid support, as employed by scales like chemistry balances where critical components are loaded only while weighing, might seem to offer a satisfactory solution, but test at tomato inspection stations showed that such systems were too complicated and required too many operator steps in the weighing cycle.
Other important considerations for tomato weighing systems are the need for damage-free handling and for obtaining even distribution of the fruit in the weigh hopper, since asymmetrical loading causes lateral forces that can lower system accuracy through vertical frictional forces.
It is desirable to provide a system that can employ the conventional sample box to transport the sample from the bulk load sampler to the mechanical grading table. At some inspection stations, the space available for the weighing system is nearly as small as the sample box. Moreover, the system should permit either front or side entry of the sample box. Current inspection systems also prefer to continue the procedure of dividing each sample of fruit substantially equally for two distinct types of inspection, scales being used to weigh the half that is graded for defects while weighing is unnecessary for the other half.
An overall consideration is the need for simplicity of design and operation and for employing a minimum number of components in order to assure reliability and low cost. The system's accuracy must, of course, meet or exceed applicable State regulations, and must consider the operators' safety, capabilities, and motivations. The operating rate should be rapid, preferably consuming no more than two minutes per four-sample load. The system needs to be durable and accurate for 40,000 cycles per season for at least five seasons. It should also result in minimum damage to the fruit. The equipment should be easy to manufacture, install, maintain, and clean. There should be no complicated lifting or dumping devices. Finally, the peak shock loads on the load cell should not exceed twice the sample weight.
The objects of the present invention include solving the problems set forth above and meeting the requirements and considerations stated there.
In addition, the invention has the objects of: providing for suitable sample dumping of the sample box while sending approximately half of the contents of the sample box into the weigh hopper and half onto a conveyor for the sample portion that does not need to be weighed; suspending the overhead load cell in an improved manner; protecting the load cell from shock; providing adjustment for the suspension lines by which the weigh hopper is suspended from the load cell; providing the weigh hopper suspension with dampening to limit swing and accelerate the actual weighing while substantially eliminating the friction occasioned by the dampening; providing for smooth and gentle but effective release of the fruit from the weigh hopper to a conveyor close below it; providing a simple but rapid and effective system for determining the grade defect percentages for each sample; providing clear instructions for the operators at each stage; and producing complete and clear information about each important factor.
Other objects and advantages of the invention will appear from the following description.